A component mounter for mounting electronic components such as semiconductors on a board is equipped with a component feeder carriage in which numerous parts feeders such as tape feeders for storing components are aligned.
The component mounter repeats the mounting operation of picking up components from these parts feeders using its transfer head, and placing them on the board. In order to improve the efficiency of this mounting operation, multi-nozzle transfer head, in which two or more suction nozzles for holding components are aligned, is often used. Conventional alignment of suction nozzles in the multi-nozzle transfer head includes the series nozzle type, in which two or more suction nozzles are aligned linearly in a single line; and the rotary type in which two or more suction nozzles are disposed circumferentially.
The mounting operation takes place by moving the transfer head by using a moving device such as an XY table. However, the moving shafts composing the XY table incorporate mechanical error caused by pitch error of the ball screw.
Accordingly, the move command value for each shaft from the controller does not always result in the actual position being attained. Positional deviation specific to each point on the board exists. The mounter thus executes calibration for identifying the positional deviation specific to each mounting point on the board in advance to compensate for the deviation. More specifically, a board recognition camera captures an image of a calibration board in which calibration measuring points are provided on a grid at the time of machine startup and maintenance. The position of each measuring point detected by capturing the image is compared with the position in the control data for identifying the dislocation unique to each mounting point. During the actual mounting operation, the moving device is driven while compensating for the identified dislocation.
However, a conventional transfer head as described above has the following disadvantages in mounter structure and mounting efficiency.
First, the series nozzle type requires greater alignment length with increasing number of nozzles. This leads to a longer horizontal movement stroke for moving the transfer head within the mounter, increasing machine space and costs. In addition, a larger number of nozzles unavoidably results in buildup of pitch error between suction nozzles. Larger pitch error causes more frequent suction errors while vacuum-holding two or more components picked up at the same time from the component feeder carriage (multiple parts feeders) by two or more suction nozzles. The resulting failure of simultaneous component pickup may reduce mounting efficiency. This lower feasibility of simultaneous pickup is also a disadvantage of the rotary transfer head.
Second, many different types of components are mounted on the same board, and shapes and sizes also differ. Accordingly, the suction nozzle which vacuum-holds and picks up these components need to be designed to pick up specific types of components. However, it is difficult to efficiently dispose two or more suction nozzles for components with different sizes and shapes in a conventional multi-nozzle transfer head. This restricts the types of components that can be mounted using the same mounter, impeding the improvement of mounting efficiency.
Third, a multi-nozzle transfer head also requires the aforementioned calibration process. However, a complete set of calibration data may not be obtainable depending on where the camera is positioned on the series nozzle transfer head when the board recognition camera installed in the series nozzle transfer head is used for calibration.